Riddle: You have 12 pills and they all got the same weight, except for one, which hasn't got the same weight. You don't know if it is heavier or easier. You have one scale to weight the pills. You now have to find out, which pill is the right one (the one with a different weight), but you can use the scale only three times. How do you know, which one is the right one?
Answer: E=easier in "1", H=heavier in "1".
1: Weight 4:4. If they balance go to "2", if they don't balance, go to "3".
2: Balance 1:1 of the pills you didn't weight yet. Then weight one you didn't weight and one you did weight. If they balanced in the first weighing, and balanced in the second weighing, the last pill is the right one. If they balanced in the first weighing and dind't balance in the second, the one you didn't use before is the right pill. If they didn't balance at all, it's the pill you weighed twice. If they didn't balance in the first weighing, but balanced in the second, it is the first pill.
3:Weight EHH:EHH. If they balance, weight one you already weighed, with an unweighed and go to "4". If they don't balance go to "5".
4: If they balance, the one you didn't weight at all is the right pill. If they don't balance, the one you only weighed once is the right one.
5: Give away every pill that was once easier AND once heavier. You should only have EHH left. Weight H:H. If they balance, E is the right one. If the don't balance, the one which was only heavier the whole time, is the right pill.